Abstract
During operation, the shear friction between the silicone oil and the plates of a viscous coupling (VC) will generate heat and increase the temperature of the silicone oil, inflate the volume, increase the internal pressure, and eventually deliver more torque, in what is called hump operation mode. Temperature is the root cause of the change of the operation characteristics in VCs. In this paper, the heat-transfer model for a VC is established based on the thermodynamical theory. The capacity of the heat transmission of each part of the VC are calculated to obtain the temperature of silicone oil. The real-time shear torque of the VC is finally obtained. Then, the theoretical analysis on hump phenomenon was done. The internal pressure was obtained by analyzing the characteristics of ideal gas, and the maximum torque during the hump phenomenon was calculated. The simulation of the key parameters and the entire working process for the VC were carried out based on the proposed calculation model. A prototype of a viscous limited-slip differential (VLSD) was developed to test the output torque characteristics. The test results were quite consistent with the simulation results, and the accuracy of the calculation model was verified.
Highlights
A viscous coupling (VC) is a torque-transmission device that uses the shearing force of high-viscosity fluid
The main reason for the differences is that the plates in the VC are movable duroperation, which waswas ignored in the calculation model
The rising temperature of the silicone oil is the basis of the change in operating characteristics of the VC
Summary
A VC is a torque-transmission device that uses the shearing force of high-viscosity fluid. If a VC operates at a large speed difference for a long period of time, the generated heat will continue to increase the internal pressure and temperature, and eventually form a quasi-rigid connection of the driving and driven plates, the delivering torque will increase sharply, and the VC moves into hump operation mode [1]. Only by performing an accurate analysis of the absorbed heat and the temperature of the silicone oil, the real-time characteristics of the VC can be predicted accurately. This is one of the most important aspects of VCs, and the problem to be resolved in this paper
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